Holocene precipitation changes in the Maya forest, Yucatán peninsula, Mexico

Holocene fossil pollen samples (n = 38) from Lake Silvituc in Mexico were analyzed with the analog technique using modern pollen samples (n = 98) of the Yucatán Peninsula, Mexico. Calculated dissimilarity indices allow us to reconstruct the vegetation and to develop a precipitation record for the last 7900 years. The Middle Holocene shows a gradual increase of precipitation and a marked drop in reconstructed precipitation around 4200 BCE. During the Late Holocene two phases were identified: Phase I (2500 BCE - 1 CE) shows the greatest increase in precipitation with four peaks around 1200 BCE, 650 BCE, 200 BCE and 1 CE. Also a period of increased precipitation resulted for the period between 200 and 500 BCE. Periods of reduced precipitation were detected at 900-1100 BCE, 500-600 BCE and 100-190 BCE. Phase II (1-2000 CE) encompasses several strong dry events during the following periods: 150-300 CE, 750-900 CE, 1050-1180 CE, and 1530-1580 CE. A strong reduction of 32% in precipitation in the late Preclassic Period (100-300 CE) was detected. Non-analogs of Phase II are associated with periods of reduced precipitation and fall into time periods of extended droughts related to the Maya Late Classic and the Little Ice Age. A limiting factor on the use of analogs for tropical forests is that a combination of different analogs for the same fossil pollen signal exists. Interpretation under these circumstances requires good knowledge of the ecology of the taxa and a priori characterization of the modern samples.